Submarine landslide, a prevalent marine geohazard, poses a significant threat to offshore engineering facilities and often precipitates secondary disasters, including tsunamis. This study presents a three-dimensional numerical model for submarine landslides, leveraging the Smoothed Particle Hydrodynamics (SPH) method and GPU parallel technology. First, the proposed SPH model undergoes validation using the experimental data on underwater landslides. The simulation results of the water surface and soil profiles, captured at crucial moments, align with experimental observations, indicating the applicability of the proposed model. Furthermore, our investigation delves into the influence of topographic conditions on the submarine sliding process. Notably, the results show that compared with the obstacles on the surface, the trough on the surface has a greater effect on the soil flow.